Freezing processes in porous media such as concrete are multifaceted. Since the seminal work of T C Powers and co-workers was published, starting well over 50 years ago (Powers, 1945, 1949, 1975; Powers and Helmuth, 1953) many different theories have been advanced to account for various features of the observed phenomena. These include important contributions by a number of researchers, for example Litvan (1972, 1973, 1980), Fagerlund (1992), Marchand et al. (1994), and Setzer (1976, 1997). The origins of freeze-thaw damage in any one incidence of concrete degradation may be based on a combination of actions described in the various theories. An appreciation of the freeze-thaw durability issue involves consideration of a number of phenomena of which the following are believed to be the most important:
· the effect of temperature on volume
· the influence of freezing on redistribution of solute concentrations
· the influence of pore size on the freezing temperature of pore liquids
· the relationship between flow and pressure.